Thermoplastic elastomer composition

ABSTRACT

An object of the present invention is to provide a thermoplastic elastomer composition which is highly flexible while maintaining vibration damping properties, as a feature of an isobutylene polymer, and is excellent in moldability and rubber-like properties, and also has particularly improved permanent compression set. The object is achieved by a thermoplastic elastomer composition comprising (A) a composition obtained by crosslinking an isobutylene polymer having an alkenyl group at the molecular ends with a hydrosilyl group-containing compound while melt-kneading in the presence of at least one kind selected from an aromatic vinyl-containing thermoplastic elastomer and an olefinic resin, and (B) at least one kind selected from the group consisting of an aromatic vinyl-containing thermoplastic elastomer and an olefinic resin.

TECHNICAL FIELD

The present invention relates to a novel thermoplastic elastomercomposition which is highly flexible while maintaining vibration dampingproperties, as a feature of an isobutylene polymer, and is excellent inmoldability and rubber-like properties, and also has particularlyimproved permanent compression set.

BACKGROUND ART

As a polymer material having elasticity, those obtained by mixingrubbers such as natural and synthetic rubbers with crosslinking agentsand reinforcers and crosslinking the mixture at high temperature underhigh pressure have commonly been used, heretofore. However, theserubbers require the step of crosslinking and molding at high temperatureunder high pressure for a long time and are therefore inferior inprocessability. Since the crosslinked rubbers exhibit nothermoplasticity, recycle molding can not be conducted, unlikethermoplastic resins. Therefore, there have recently been developedvarious thermoplastic elastomers which can be easily processed intoformed articles by employing common melt-molding techniques such ashot-press molding, injection molding, and extrusion molding in the samemanner as in case of conventional thermoplastic resins. As thesethermoplastic elastomers, various polymers such as olefinic, urethane,ester, styrene and vinyl chloride polymers have been developed and areput on the market at present.

Among these polymers, styrenic thermoplastic elastomers are highlyflexible and are excellent in rubber elasticity at normal temperature.As these styrenic thermoplastic elastomers, for example, there have beendeveloped styrene-butadiene-styrene block copolymer (SBS) andstyrene-isoprene-styrene block copolymer (SIS);styrene-ethylenebutylene-styrene block copolymer (SEBS) andstyrene-ethylenepropylene-styrene block copolymer (SEPS) obtained byhydrogenating the above polymers. However, these block copolymers wereinsufficient in permanent compression set.

Also Kohyo Publication (National Publication of Translated Version) ofWO93/14135 discloses an isobutylene block copolymer comprising a polymerblock composed mainly of isobutylene and a polymer block composed mainlyof an aromatic vinyl compound as a thermoplastic elastomer which ishighly flexible and is excellent in rubber elasticity at normaltemperature, and is also excellent in vibration damping properties, gasbarrier properties and hermetical sealing properties as features of anisobutylene polymer. However, this isobutylene block copolymer is alsoinsufficient in permanent compression set, like the above-describedstyrenic thermoplastic elastomers.

As a technique for improving the permanent compression set of thisisobutylene block copolymer, Kohyo Publication (National Publication ofTranslated Version) of WO98/14518 discloses a thermoplastic polymercomposition comprising an isobutylene block copolymer containing apolymer block composed mainly of isobutylene, and crosslinked article ofa rubber, while Japanese Unexamined Patent Publication (Kokai) No.11-293083 discloses a composition comprising an isobutylene blockcopolymer, a crystalline polyolefin and a plasticizer (softener).Although these composition have improved permanent compression set whilemaintaining features of the isobutylene polymer, thermoplastic elastomercompositions having more excellent permanent compression set arerequired.

DISCLOSURE OF THE INVENTION

In light of the above-described problems of the prior art, an object ofthe present invention is to provide a thermoplastic elastomercomposition which is excellent in vibration damping properties, as afeature of an isobutylene polymer, and has satisfactory flexibility,moldability and rubber-like properties, and also has improved permanentcompression set.

The present inventors have intensively studied and completed the presentinvention. Therefore, the present invention is directed to athermoplastic elastomer composition comprising (A) a compositionobtained by crosslinking an isobutylene polymer having an alkenyl groupat the molecular ends with a hydrosilyl group-containing compound whilemelt-kneading in the presence of at least one kind selected from thegroup consisting of an aromatic vinyl-containing thermoplastic elastomerand an olefinic resin, and (B) at least one kind selected from the groupconsisting of an aromatic vinyl-containing thermoplastic elastomer andan olefinic resin.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the content of at least onekind selected from the group consisting of an aromatic vinyl-containingthermoplastic elastomer and an olefinic resin is from 5 to 100 parts byweight based on 100 parts by weight of the isobutylene polymer having analkenyl group at the molecular ends in the component (A).

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the content of the component(B) is from 5 to 100 parts by weight based on 100 parts by weight of thetotal amount of the component (A).

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition which further contains a softener(C) in the amount of 1 to 300 parts by weight based on 100 parts byweight of the isobutylene polymer having an alkenyl group at themolecular ends in the component (A).

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein an allyl group is introducedinto the molecular ends of the isobutylene polymer having an alkenylgroup at the molecular ends in the component (A) by a substitutionreaction of allyltrimethylsilane and chlorine.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the isobutylene polymerhaving an alkenyl group at the molecular ends in the component (A) is apolymer which has a number average molecular weight of 1,000 to 500,000and has at least 0.2 alkenyl groups per one molecule at the molecularends.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the isobutylene polymerhaving an alkenyl group at the molecular ends in the component (A) is apolymer having 50% by weight or more of isobutylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the aromaticvinyl-containing thermoplastic elastomer in the components (A) and (B)is a block copolymer comprising a polymer block (a) composed mainly ofan aromatic vinyl compound and a polymer block (b) composed mainly ofisobutylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the aromaticvinyl-containing thermoplastic elastomer in the components (A) and (B)is a block copolymer is a triblock copolymer which has a structurecomprising a polymer block (a) composed mainly of an aromatic vinylcompound—a polymer block (b) composed mainly of isobutylene—a polymerblock (a) composed mainly of an aromatic vinyl compound, and has aweight average molecular weight of 40,000 to 200,000.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (A) is polypropylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (A) is polyethylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (B) is polypropylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (B) is polyethylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (A) is random polypropylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (A) is high-density polyethylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (B) is random polypropylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the olefinic resin in thecomponent (B) is high-density polyethylene.

Preferred embodiment of the present invention is directed to athermoplastic elastomer composition wherein the softener (C) isparaffinic oil.

The thermoplastic elastomer composition of the present inventioncomprises (A) a composition obtained by crosslinking an isobutylenepolymer having an alkenyl group at the molecular ends with a hydrosilylgroup-containing compound while melt-kneading in the presence of atleast one kind selected from the group consisting of an aromaticvinyl-containing thermoplastic elastomer and an olefinic resin, and (B)at least one kind selected from the group consisting of an aromaticvinyl-containing thermoplastic elastomer and an olefinic resin.

The isobutylene polymer having an alkenyl group at the molecular endsused in the present invention is a polymer wherein isobutylene accountsfor 50% by weight or more, preferably 70% by weight or more, and morepreferably 90% by weight or more, of the isobutylene polymer. Themonomer other than isobutylene in the isobutylene polymer is notspecifically limited as far as it is a cationically polymerizablemonomer component, and examples thereof include aromatic vinyls;aliphatic olefins; dienes such as isoprene, butadiene, anddivinylbenzene; vinyl ethers; and β-pinene. These monomers may be usedalone, or two or more kinds of them may be used in combination.

The number average molecular weight of the isobutylene polymer is notspecifically limited, but is preferably from 1,000 to 500,000, andparticularly preferably from 5,000 to 200,000. When the number averagemolecular weight is less than 1,000, satisfactory mechanical propertiesare not achieved. On the other hand, it exceeds 500,000, moldabilitydrastically deteriorates.

The alkenyl group of the isobutylene polymer having an alkenyl group atthe molecular ends is not specifically limited as far as it is a grouphaving a carbon-carbon double bond which is active to a crosslinkingreaction with a hydrosilyl group-containing compound. Specific examplesthereof include aliphatic unsaturated hydrocarbon groups such as vinylgroup, allyl group, methylvinyl group, propenyl group, butenyl group,pentenyl group, and hexenyl group; and cyclic unsaturated hydrocarbongroups such as cyclopropenyl group, cyclobutenyl group, cyclopentenylgroup, and cyclohexenyl group.

Examples of the method of introducing an alkenyl group into themolecular ends of an isobutylene polymer includes methods of reacting apolymer having a functional group such as hydroxyl group with a compoundhaving an unsaturated group, thereby to introduce the unsaturated groupinto the polymer, as disclosed in Japanese Unexamined Patent Publication(Kokai) No. 3-152164 and Japanese Unexamined Patent Publication (Kokai)No. 7-304909. Examples of the method of introducing an unsaturated groupinto a polymer having a halogen atom include a method of conducting aFriedel-Crafts reaction with an alkenyl phenyl ether, a method ofconducting a substitution reaction with allyltrimethylsilane in thepresence of Lewis acid, and a method of conducting a Friedel-Craftsreaction with various phenols, thereby to introduce a hydroxyl group andconducting the alkenyl group-introducing reaction described above.Furthermore, as disclosed in U.S. Pat. No. 4,316,973, JapaneseUnexamined Patent Publication (Kokai) No. 63-105005 and JapaneseUnexamined Patent Publication (Kokai) No. 4-288309, the unsaturatedgroup can be introduced during the polymerization of the monomer. Amongthese methods, the method of introducing an allyl group into themolecular ends by the substitution reaction of allyltrimethylsilane andchlorine is preferable in view of reactivity.

Although the amount of the alkenyl group at the molecular ends of theisobutylene polymer can be selected optionally according to the requiredproperties, the isobutylene polymer is preferably a polymer having atleast 0.2 alkenyl groups per one molecule at the molecular ends in viewof permanent compression set after crosslinking. When the isobutylenepolymer has less than 0.2 alkenyl groups, satisfactory effect ofimproving permanent compression set by crosslinking is not exertedsometimes.

The aromatic vinyl-containing thermoplastic elastomer used in thepresent invention includes, but are not limited to, a random copolymerand a block copolymer, and is preferably a block copolymer comprising apolymer block (a) composed mainly of an aromatic vinyl compound and apolymer block (b) composed mainly of isobutylene. The aromaticvinyl-containing thermoplastic elastomer is preferably a block copolymercomprising a polymer block (a) composed mainly of an aromatic vinylcompound and a polymer block (c) composed mainly of a conjugated dienecompound, and a block copolymer obtained by hydrogenating the blockcopolymer. Among these block copolymers, a triblock copolymer comprisinga polymer block (a) composed mainly of an aromatic vinyl compound—apolymer block (b) composed mainly of isobutylene—a polymer block (a)composed mainly of an aromatic vinyl compound is particularly preferablebecause the tensile strength increases.

The polymer block composed mainly of isobutylene as used herein refersto a block wherein isobutylene accounts for 50% by weight or more,preferably 70% by weight or more, and more preferably 90% by weight, ofthe polymer block. The monomer other than isobutylene in the polymerblock composed mainly of isobutylene is not specifically limited as faras it is a cationically polymerizable monomer component, and examplesthereof include aromatic vinyls; aliphatic olefins; dienes such asisoprene, butadiene, and divinylbenzene; vinyl ethers; and β-pinene.These monomers may be used alone, or two or more kinds of them may beused in combination.

Examples of the aromatic vinyl compound include styrene,α-methylstyrene, β-methylstyrene, p-methylstyrene, t-butylstyrene,monochlorostyrene, dichlorostyrene, methoxystyrene, indene,divinylbenzene, N,N-dimethyl-p-aminoethylstyrene,N,N-diethyl-p-aminoethylstyrene, and vinylpyridine. Among thesecompounds, styrene, α-methylstyrene, p-methylstyrene and indene arepreferable in view of balance between cost, physical properties andproductivity, and two or more kinds may be selected from thesecompounds.

Examples of the conjugated diene compound include 1,3-butadiene,isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene,2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene,3-butyl-1,3-octadiene, and chloroprene. In order to obtain ahydrogenated diene polymer which can be employed in the industrial fieldand is excellent in physical properties, 1,3-butadiene, isoprene and1,3-pentadiene are preferable, and 1,3-butadiene and isoprene areparticularly preferable.

The proportion of the aromatic vinyl compound in the aromaticvinyl-containing thermoplastic elastomer is not specifically limited,but is preferably from 5 to 80% by weight, and particularly preferablyfrom 10 to 40% by weight, in view of balance between physical propertiesand processability.

Also the number average molecular weight of the aromaticvinyl-containing thermoplastic elastomer is not specifically limited,but is preferably from 15,000 to500,000, and particularly preferablyfrom 40,000 to 200,000. When the number average molecular weight is lessthan 15,000, mechanical properties such as tensile properties may becomeinsufficient. On the other hand, when it exceeds 500,000, moldabilitymay drastically deteriorate.

The olefinic resin used in the present invention is a homopolymer orcopolymer containing a monomer selected from ethylene and α-olefinhaving 3 to 20 carbon atoms as a main component. Examples thereofinclude polyethylene (high-density polyethylene, low-densitypolyethylene, linear low-density polyethylene), polypropylene(isotactic-homopolypropylene, random polypropylene, blockpolypropylene,syndiotactic-homopolypropylene), poly-1-butene, ethylene-propylenecopolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, andethylene-1-octene copolymer. In view of heat resistance, polypropyleneand polyethylene each having crystallinity are preferable. In view ofmechanical properties, random polypropylene is most preferable. In viewof permanent compression set, high-density polyethylene is mostpreferable.

In the present invention, the isobutylene polymer having an alkenylgroup at the molecular ends forms a composition obtained by crosslinkingwith a hydrosilyl group-containing compound while melt-kneading in thepresence of at least one kind selected from the group consisting of anaromatic vinyl-containing thermoplastic elastomer and an olefinic resin.Such a technique is generally referred to as dynamic crosslinking and ischaracterized in that a polymer network produced by proceeding of thecrosslinking reaction while melt-kneading is cleaved by a shear forceand exhibits thermoplasticity even after crosslinking, unlikeconventional chemical crosslinking (static crosslinking). Theisobutylene polymer usually has no functional group for crosslinking anda decomposition reaction may occur in a radical reaction employedcommonly as a crosslinking reaction. In the present invention,introduction of an alkenyl group into the molecular ends of theisobutylene polymer enables a hydrosilylation reaction and also enablesa crosslinking reaction which uses a hydrosilyl group-containingcompound as a crosslinking agent. This hydrosilylation reaction has suchan advantage that by-products are not produced and unnecessary sidereaction does not arise.

In the present invention, the hydrosilyl group-containing compoundrequired to obtain a crosslinked article of the isobutylene polymerhaving an alkenyl group at the molecular ends is not specificallylimited and various compounds can be used. For example, there can beused linear polysiloxanes represented by the following general formula(I) or (II):R¹ ₃SiO—[Si(R¹)₂O]_(a)—[Si(H)(R²)O]_(b)—[Si(R²)(R^(3)O]) _(c)—SiR¹₃  (I)HR¹ ₂SiO—[Si(R¹)₂O]_(a)—[Si(H)(R²)O]_(b)—[Si(R²)(R³)O]_(c)—SiR¹ ₂H  (II)wherein R¹ and R² represents an alkyl group having 1 to 6 carbon atoms,or a phenyl group; R³ represents an alkyl or aralkyl group having 1 to10 carbon atoms; and a, b and c represent integers which satisfy therelations: 0≦a≦100, 2≦b≦100, and 0≦c≦100, and cyclic siloxanesrepresented by the following general formula (III):

wherein R⁴ and R⁵ represent an alkyl group having 1 to 6 carbon atoms,or a phenyl group; R⁶ represents an alkyl or aralkyl group having 1 to10 carbon atoms; and d, e and f represent integers which satisfy therelations: 0≦d≦8, 2≦e≦10, and 0≦f≦8, and also satisfy the relation:3≦d+e+f≦10. In view of good compatibility, among the above compoundshaving a hydrosilyl group (Si—H group), preferred are compoundsrepresented by the following the general formula (IV):

wherein g and h represent integers which satisfy the relations: 2≦g+h≦50and 2≦g, 0≦h; R⁷ represents a hydrogen atom or a methyl group; R⁸represents a hydrocarbon group having 2 to 20 carbon atoms and mayoptionally have one or more aromatic rings; and i represents an integerwhich satisfies the relation: 0≦i≦5.

While isobutylene polymer having an alkenyl group at the molecular endsand the hydrosilyl group-containing compound can be mixed in any ratio,a molar ratio of an alkenyl group to a hydrosilyl group is preferablywithin a range from 5 to 0.2, and more preferably from 2.5 to 0.4, inview of reactivity. When the molar ratio is more than 5, the resultingproduct is tacky and has poor permanent compression set because ofinsufficient crosslinking. On the other hand, when it is less than 0.2,since many active hydrosilyl groups are remained after crosslinking, ahydrogen gas is evolved by hydrolysis and the resulting crosslinkedproduct may cause cracks and voids.

The crosslinking reaction of the isobutylene polymer and the hydrosilylgroup-containing compound proceeds when two components are mixed andheated, and the reaction can be remarkably promoted by the addition of acrosslinking catalyst (hydrosilylation catalyst). The crosslinkingcatalyst is not specifically limited and examples thereof includeradical initiators such as organic peroxides and azo compounds, andtransition metal catalysts.

The radical initiator is not specifically limited and examples thereofinclude dialkyl peroxides such as di-t-butyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, dicumyl peroxide, t-butylcumyl peroxide, andα,α′-bis (t-butylperoxy)isopropylbenzene; acyl peroxides such as benzoylperoxide, p-chlorobenzoyl peroxide, m-chlorobenzoyl peroxide,2,4-dichlorobenzoyl peroxide, and lauroyl peroxide; peracid esters suchas t-butyl perbenzoate; peroxydicarbonates such as diisopropylperoxydicarbonate and di-2-ethylhexyl peroxydicarbonate; peroxyketalssuch as 1,1-di(t-butylperoxy)cyclohexane and1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane; and azo compounds suchas 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile,1,1′-azobis-1-cyclohexanecarbonitrile,2,2′-azobis(2,4-dimethylvaleronitrile), and2,2′-azosiobutyrovaleronitrile.

Also the transition metal catalyst is not specifically limited andexamples thereof include platinum metal; those obtained by dispersingsolid platinum in carries such as alumina, silica and carbon black;chloroplatinic acid; complexes of chloroplatinic acid with alcohol,aldehyde or ketone; and platinum-olefin complexes, andplatinum(0)-dialkenyltetramethyldisiloxane complexes. Examples of thecatalyst other than platinum compounds include RhCl(PPh₃)₃, RhCl₃,RuCl₃, IrCl₃, FeCl₃, AlCl₃, PdCl₂.H₂O, NiCl₂, and TiCl₄. These catalystsmay be used alone, or two or more kinds of them may be used incombination. Among these catalysts, platinumvinylsiloxane is mostpreferable in view of compatibility, crosslinking efficiency and scorchstability.

The amount of the catalyst is not specifically limited, but ispreferably within a range from 10⁻¹ to 10⁻⁸ mol, and more preferablyfrom 10⁻³ to 10⁻⁶ mol, per mol of the alkenyl group of the isobutylenepolymer. When the amount is less than 10⁻⁸ mol, crosslinking may notproceed sufficiently. On the other hand, when the amount is more than10⁻¹ mol, a remarkable effect is not exerted and, therefore, the amountis preferably less than 10⁻¹ mol in view of economy.

In the present invention, the amount of at least one kinds selected fromthe group consisting of the aromatic vinyl-containing thermoplasticelastomer and the olefinic resin in the component (A) is from 0.5 to 900parts by weight, and preferably from 5 to 100 parts by weight, based on100 parts by weight of the isobutylene polymer having an alkenyl groupat the molecular ends. When the amount exceeds 900 parts by weight,permanent compression set may deteriorates. On the other hand, when theamount is 100 parts by weight or less, since the concentration of thealkenyl group is sufficiently high, the reaction rate of thecrosslinking reaction is preferably high. On the other hand, when theamount is less than 0.5 parts by weight, moldability may drasticallydeteriorate.

The composition, as the component (A) of the present invention, which isobtained by crosslinking an isobutylene polymer having an alkenyl groupat the molecular ends with a hydrosilyl group-containing compound whilemelt-kneading in the presence of at least one kind selected from thegroup consisting of an aromatic vinyl-containing thermoplastic elastomerand an olefinic resin, can be produced by the method described below.

In case the composition is produced by a closed or open type batch-wisekneading apparatus, such as Labo Plastomill, Brabender, Banbury mixer,kneader, or roll, all components other than a crosslinking agent arepreviously mixed, charged in a kneading apparatus and then melt-kneadeduntil a homogeneous mixture is obtained. The crosslinking agent is addedand, after the crosslinking reaction proceeds sufficiently,melt-kneading is terminated.

In case the composition is produced by using a continuous melt-kneadingapparatus such as single-screw extruder or twin-screw extruder, allcomponents other than a crosslinking agent are melt-kneaded by amelt-kneading apparatus such as extruder until a homogeneous mixture isobtained and the mixture is pelletized. After dry-blending the pelletswith the crosslinking agent and the dry blend is further melt-kneaded bya melt-kneading apparatus such as extruder or Banbury mixer, thereby todynamically crosslink the isobutylene polymer having an alkenyl group atthe molecular ends. Alternatively, all components other than acrosslinking agent are melt-kneaded by a melt-kneading apparatus such asextruder and, after adding the crosslinking agent through anintermediate section of a cylinder of the extruder, the mixture isfurther melt-kneaded, thereby to dynamically crosslink the isobutylenepolymer having an alkenyl group at the molecular ends.

The melt-kneading is preferably conducted at a temperature within arange from 140 to 210° C., and more preferably from 150 to 200° C. Whenthe melt-kneading temperature is lower than 140° C., the aromaticvinyl-containing thermoplastic elastomer and the olefinic resin are notmelted and may not mixed sufficiently. On the other hand, when themelt-kneading temperature is higher than 210° C., the isobutylenepolymer may be thermally decomposed.

The present invention is characterized by further mixing a dynamicallycrosslinked composition as the component (A) with at least one kindselected from the group consisting of an aromatic vinyl-containingthermoplastic elastomer and an olefinic resin as the component (B). Sucha two-stage step has such an advantage that the proportion of theisobutylene polymer having an alkenyl group at the molecular ends in thestage of producing the component (A), thereby making it possible toincrease the reaction rate of the crosslinking reaction. In case asoftener is added as the component (C), remarkable advantage isobtained. Although optimum reaction conditions vary depending on thekind and molecular weight of the aromatic vinyl-containing thermoplasticelastomer and olefinic resin in the component (A), a two-stage stepmakes it possible to control properties of the finally obtainedthermoplastic elastomer composition within a wide range by selecting thekinds and molecular weights of the component (B), while the kind andmolecular weight of the aromatic vinyl-containing thermoplasticelastomer and olefinic resin used in the production of the component (A)are the same. It is also possible to mix a component having a functionalgroup which adversely affects the crosslinking reaction.

In invention, the amount of at least one kind selected from the groupconsisting of the aromatic vinyl-containing thermoplastic elastomer andthe olefinic resin, as the component (B), is preferably from 5 to 200parts by weight, and more preferably from 5 to 100 parts by weight,based on 100 parts by weight of the total amount of the component (A).When the amount of the component (B) exceeds 200 parts by weight,permanent compression set may drastically deteriorate. On the otherhand, when the amount is less than 5 parts by weight, moldability maydrastically deteriorate.

In case of melt-kneading the component (A) of the present invention withthe component (B), a known method may be employed and theabove-described batch-wise kneading apparatus and continuous kneadingapparatus can be used. For example, there can be used a method ofweighing the components (A) and (B), mixing them using a tumbler, aHenschel mixer or a ribbon blender, and melt-kneading the mixture usingan extruder, a Banbury mixer or a roll. The kneading temperature is notspecifically limited, but is preferably within a range from 100 to 250°C., and more preferably from 150 to 220° C. When the kneadingtemperature is lower than 100° C., the kneaded mixture may not besufficiently melted. On the other hand, when the kneading temperature ishigher than 250° C., deterioration by heat may initiate.

To the composition of the present invention, a softener (C) can be addedto improve moldability and flexibility, in addition to the components(A) and (B). As the softener, mineral oil for use in the processing ofrubber or a liquid or low-molecular weight synthetic oil can be used.The softener and plasticizer are often used in the same meaning and arenot specifically identified in the present invention.

Examples of the mineral oil include paraffinic oil, naphthenic oil, andaromatic high-boiling petroleum fraction. Among these mineral oils,preferred is paraffinic oil which does adversely affect the crosslinkingreaction. Examples of the liquid or low-molecular weight synthetic oilinclude polybutene, hydrogenated polybutene, liquid polybutadiene,hydrogenated liquid polybutadiene, and liquid poly (α-olefins). Thesesofteners may be used alone, or plural softeners may be used incombination.

The amount of the softener (C) is preferably from 1 to 300 parts byweight based on 100 parts by weight by of the isobutylene polymer havingan alkenyl group at the molecular ends. When the amount exceeds 300parts by weight, the resulting product may be tacky and has decreasedmechanical strength.

The composition of the present invention can contain additives such asother thermoplastic resins, thermoplastic elastomers, rubbers,stabilizers, and fillers according to the required properties forvarious purposes as far as the physical properties are not adverselyaffected. Examples of the thermoplastic resin include polyolefinmodified with maleic acid, maleic anhydride or glycidyl methacrylate,polymethylpentene, cyclic olefin (co)polymer, polystyrene, polyphenyleneether, polyamide, polyester, polyurethane, polycarbonate, ABS resin,polymethyl methacrylate, and polyvinyl chloride. Examples of thethermoplastic elastomer include olefinic, vinyl chloride, urethane,ester, and amide elastomers. Examples of the rubber include naturalrubber, butadiene rubber, styrene-butadiene rubber,acrylonitrile-butadiene rubber, isoprene rubber, butyl rubber,ethylene-propylene rubber, acrylic rubber, silicone rubber, andfluororubber. Examples of the additive, which can be appropriatelymixed, include hindered phenol, phosphorus and sulfur antioxidants;hindered amine ultraviolet absorbers; photostabilizers; pigments;surfactants; flame retardants; blocking inhibitors; antistatic agents;lubricants; silicone oils; fillers; and reinforcers. Examples of theinorganic filler, among fillers, include precipitated calcium carbonate,ground calcium carbonate, other calcium filler, hard clay, soft clay,kaolin clay, talc, wet silica, dry silica, amorphous silica,wollastonite, synthetic or natural zeolite, diatomaceous earth, quartzsand, pumice powder, slate powder, alumina, aluminum sulfate, bariumsulfate, calcium sulfate, molybdenum disulfide, magnesium hydroxide,aluminum hydroxide, and those obtained by treating these inorganicfillers with a silane coupling agent. Two or more kinds of theseadditives can be used in combination. The hardness and tensile strengthcan be improved by mixing these inorganic fillers. When using metalhydroxides such as magnesium hydroxide and aluminum hydroxide as theinorganic filler, excellent flame resistance can be sometimes imparted.As the blocking inhibitor, for example, silica and zeolite arepreferable and these may be natural or synthetic blocking inhibitors,and complete spherical crosslinked particles such as crosslinked acryliccomplete spherical particles are also preferable. As the antistaticagent, N,N-bis-(2-hydroxyethyl)-alkylamines having an alkyl group having12 to 18 carbon atoms and glycerin fatty acid ester are preferable. Asthe lubricant, fatty acid metal lubricants, fatty acid amide lubricants,fatty acid ester lubricants, fatty acid lubricant, aliphatic alcohollubricant, partial ester of fatty acid and polyhydric alcohol, andparaffinic lubricant are preferably used. Two or more kinds selectedfrom them may be used in combination.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be illustrated by the following exampleswhich do not limit the present invention.

Before presenting the examples, various methods for measurement andvarious methods for evaluation are described.

(Hardness)

In accordance with JIS K 6352, a 12.0 mm thick pressed sheet was used asa test piece.

(Permanent Compression Set)

In accordance with JIS K 6262, a 12.0 mm thick pressed sheet was used asa test piece. The measurement was conducted under the conditions of 25%deformation at 70° C. for 22 hours or at 100° C. for 22 hours.

(Tensile Properties)

Tensile properties were determined in the following manner. Inaccordance with JIS K 6251 (Tensile Test Method of Vulcanized Rubber), a2.0 mm thick pressed sheet was punched out to form a JIS No. 3 dumbbelltest piece which was tested under the conditions of a stretching rate of500 mm/min at 23° C. Autograph AG-10TB (manufactured by ShimadzuCorporation) was used as a measuring apparatus.

(Vibration Damping Properties)

Vibration damping properties were evaluated by dynamic viscoelasticity.In accordance with JIS K 6394 (Testing Method for Dynamic Properties ofVulcanized Rubber and Thermoplastic rubber), two test pieces measuring 5mm long×6 mm wide×2 mm thick were cut out and the measurement wasconducted at a shear mode under the conditions of a frequency of 10 Hzand strain of 0.05%. A dynamic viscoelasticity measuring apparatusDVA-200 (manufactured by IT Instrument Control Co., Ltd.) was used.Vibration damping properties were evaluated by the tan δ value. Thelarger this value, the better vibration damping properties.

(Abbreviations of Components Described in Examples)

APIB: polyisobutylene having an allyl group at the molecular ends(Production Example 1)

SIBS1: styrene-isobutylene-styrene block copolymer (Production Example2)

SIBS2: styrene-isobutylene-styrene block copolymer (Production Example3)

PP1: random polypropylene, manufactured by Grand Polymer Co., Ltd. underthe trade name of “Grand Polypro J226EA”

PP2: random polypropylene, manufactured by Grand Polymer Co., Ltd. underthe trade name of “Grand Polypro J215W”

PE1: high-density polyethylene, manufactured by SumitomoMitsuiPolyolefin Co., Ltd. under the trade name of “Hizex 2200J”

PE2: low-density polyethylene, manufactured by SumitomoMitsui PolyolefinCo., Ltd. under the trade name of “Hizex L900N”

PE3: linear low-density polyethylene, manufactured by SumitomoMitsuiPolyolefin Co., Ltd. under the trade name of “Hizex UJ580”

OIL: paraffinic process oil, manufactured by Japan Energy Corporationunder the trade name of “P-500”crosslinking agent (hydrosilylgroup-containing compound): polymethylhydrogensiloxane, manufactured byGE Toshiba Silicones Co., Ltd. under the trade name of“TSF-484”Crosslinking catalyst: 3 wt % xylene solution of1,1,3,3-tetramethyl-1,3-dialkenyldisiloxane complex of platinum(0)

SEBS: styrene-ethylenebutylene-styrene block copolymer, manufactured byKraton Polymer Japan Co., Ltd. under the trade name of “Kraton G1651”

SEPS: styrene-ethylenepropylene-styrene block copolymer, manufactured byKuraray Co., Ltd. under the trade name of “Septon 4055”

(PRODUCTION EXAMPLE 1 Production of Polyisobutylene Having an AlkenylGroup at the Molecular Ends (APIB)

After replacing the atmosphere in a polymerization vessel of a 2 Lseparable flask with nitrogen, 142 mL of ethylcyclohexane (dried withmolecular sieves) and 427 mL of toluene (dried with molecular sieves)were charged using an injection syringe and the polymerization vesselwas cooled by immersing in a dry ice/methanol bath at −70° C. Then, aTeflon® delivery tube was connected to a pressure-resistant glassliquefaction sampling tube equipped with a three-way cock and containing277 mL (2934 mmol) of an isobutylene monomer and the isobutylene monomerwas delivered into the polymerization vessel under nitrogen pressure.Then, 0.85 g (3.7 mmol) of p-dicumyl chloride and 0.68 g (7.4 mmol) ofα-picoline were added, followed by the addition of 5.8 mL (52.7 mmol) oftitanium tetrachloride. The reaction mixture was stirred for 2.5 hoursafter the initiation of the polymerization, and about 1 mL of thepolymer slurry was withdrawn as a sample. Subsequently, a 75% mixedsolution of allyltrimethylsilane (1.68 g, 11 mmol) in toluene was addedin the polymerization vessel. 2 hours after the addition of the mixedsolution, a large amount of water was added to terminate the reaction.

After the reaction solution was washed twice with water and the solventwas distilled off, the resulting polymer was dried in vacuum at 60° C.for 24 hours to obtain the objective block copolymer. The molecularweight of the resulting polymer was measured by gel permeationchromatography (GPC). The resulting polymer was polyisobutylene whichhas Mn of 45,500 and Mw/Mn of 1.10 and also has an allyl group at themolecular ends. The number of allyl groups at the molecular endscalculated by NMR was 2.0 per one molecule.

(PRODUCTION EXAMPLE 2 Production of Styrene-Isobutylene-Styrene BlockCopolymer (SIBS1)

After replacing the atmosphere in a polymerization vessel of a 500 mLseparable flask with nitrogen, 95.4 mL of n-hexane (dried with molecularsieves) and 135 mL of butyl chloride (dried with molecular sieves) werecharged using an injection syringe and the polymerization vessel wascooled by immersing in a dry ice/methanol bath at −70° C. Then, aTeflon® delivery tube was connected to a pressure-resistant glassliquefaction sampling tube equipped with a three-way cock and containing54.4 mL (576 mmol) of an isobutylene monomer and the isobutylene monomerwas delivered into the polymerization vessel under nitrogen pressure.Then, 0.178 g (0.77 mmol) of p-dicumyl chloride and 0.124 g (1.42 mmol)of N,N-dimethylacetamide were added, followed by the addition of 1.69 mL(15.44 mmol) of titanium tetrachloride. The reaction mixture was stirredfor 75 minutes after the initiation of the polymerization, and about 1mL of the polymer slurry was withdrawn as a sample. Subsequently, 13.83g (132.8 mmol) of a styrene monomer was added in the polymerizationvessel. 45 minutes after the addition of the styrene monomer, a largeamount of water was added to terminate the reaction.

After the reaction solution was washed twice with water and the solventwas distilled off, the resulting polymer was dried in vacuum at 60° C.for 24 hours to obtain the objective block copolymer (SIBS1). Themolecular weight of the resulting polymer was measured by gel permeationchromatography (GPC). As a result, Mn was 64,000 and Mw/Mn was 1.2. Thestyrene content calculated by NMR was 30%.

(PRODUCTION EXAMPLE 3 Production of Styrene-Isobutylene-Styrene BlockCopolymer (SIBS2)

After replacing the atmosphere in a polymerization vessel of a 500 mLseparable flask with nitrogen, 97.6 mL of n-hexane (dried with molecularsieves) and 140.5 mL of butyl chloride (dried with molecular sieves)were charged using an injection syringe and the polymerization vesselwas cooled by immersing in a dry ice/methanol bath at −70° C. Then, aTeflon® delivery tube was connected to a pressure-resistant glassliquefaction sampling tube equipped with a three-way cock and containing47.7 mL (505.3 mmol) of an isobutylene monomer and the isobutylenemonomer was delivered into the polymerization vessel under nitrogenpressure. Then, 0.097 g (0.42 mmol) of p-dicumyl chloride and 0.073 g(0.84 mmol) of N,N-dimethylacetamide were added, followed by theaddition of 1.66 mL (15.12 mmol) of titanium tetrachloride. The reactionmixture was stirred for 75 minutes after the initiation of thepolymerization, and about 1 mL of the polymer slurry was withdrawn as asample. Subsequently, 13.71 g (131.67 mmol) of a styrene monomer wasadded in the polymerization vessel. 75 minutes after the addition of thestyrene monomer, a large amount of water was added to terminate thereaction.

After the reaction solution was washed twice with water and the solventwas distilled off, the resulting polymer was dried in vacuum at 60° C.for 24 hours to obtain the objective block copolymer (SIBS2). Themolecular weight of the resulting polymer was measured by gel permeationchromatography (GPC). As a result, Mn was 110,000 and Mw/Mn was 1.2. Thestyrene content calculated by NMR was 30%.

EXAMPLE 1

First step: After weighing 40 g of the total amount of APIB obtained inProduction Example 1 and SIBS1 obtained in Production Example 2 in theratio shown in Table 1, they were melt-kneaded for 3minutes using a LaboPlastomill (manufactured by Toyo Seiki Seisaku-Sho, Ltd.) set to 170° C.A crosslinking agent was added in the proportion shown in Table 1 and 5μl of a crosslinking catalyst was added, and then the mixture wasdynamically crosslinked at 170° C. while melt-kneading until the torquevalue reached a maximum value. The melt-kneading was conducted for 3minutes after the torque value reached a maximum value, and then adynamically crosslinked composition (component (A)) was taken out.

Second step: After weighing 40 g of the total amount of the resultingcomponent (A) and PP1 in the ratio shown in Table 1, they weremelt-kneaded for 5 minutes using a Labo Plastomill set to 170° C. and athermoplastic elastomer composition was taken out. The resultingthermoplastic elastomer composition could be easily formed into a sheetby using a hot-press (manufactured by Shinto Metal Industries, Ltd.) at190° C. The hardness, permanent compression set and tensile propertiesof the resulting sheet were measured by the methods described above. Thephysical properties of the sheets are shown in Table 1.

EXAMPLES 2 TO 5

In the same manner as in Example 1, except that the amounts of APIB,SIBS1, the crosslinking agent and the crosslinking catalyst werereplaced by the amounts shown in Table 1, thermoplastic elastomercompositions were obtained and physical properties were evaluated. Thephysical properties are shown in Table 1.

EXAMPLES 6 TO 9

In the same manner as in Example 5, except that PP2 was used as theolefinic resin and the amount of PP2 and the softener were replaced bythe amounts shown in Table 1, thermoplastic elastomer compositions wereobtained and physical properties were evaluated. The physical propertiesare shown in Table 1.

COMPARATIVE EXAMPLE 1

Using Labo Plastomill set to 170° C., 40 g of SIBS1 obtained inProduction Example 2 was melt-kneaded for 5 minutes and taken out. Then,the resulting elastomer composition was formed into a sheet by using ahot-press (manufactured by Shinto Metal Industries, Ltd.) at 190° C. Thehardness, permanent compression set and tensile properties of theresulting sheet were measured by the methods described above. Thephysical properties of the sheets are shown in Table 2.

COMPARATIVE EXAMPLE 2

After weighing 40 g of the total amount of SIBS1 and PP1 in the ratioshown in Table 2, they were melt-kneaded for 5 minutes using LaboPlastomill set to 170° C. and taken out. Then, the resulting elastomercomposition was formed into a sheet by using a hot-press (manufacturedby Shinto Metal Industries, Ltd.) at 190° C. The hardness, permanentcompression set and tensile properties of the resulting sheet weremeasured by the methods described above. The physical properties of thesheets are shown in Table 2.

COMPARATIVE EXAMPLE 3

After weighing 40 g of the total amount of SEBS, PP1 and OIL in theratio shown in Table 2, they were melt-kneaded for 5 minutes using LaboPlastomill set to 170° C. and taken out. Then, the resulting elastomercomposition was formed into a sheet by using a hot-press (manufacturedby Shinto Metal Industries, Ltd.) at 190° C. The hardness, permanentcompression set and tensile properties of the resulting sheet weremeasured by the methods described above. The physical properties of thesheets are shown in Table 2.

COMPARATIVE EXAMPLE 4

After weighing 40 g of the total amount of SEBS, PP1 and OIL in theratio shown in Table 2, they were melt-kneaded for 5 minutes using LaboPlastomill set to 170° C. and taken out. Then, the resulting elastomercomposition was formed into a sheet by using a hot-press (manufacturedby Shinto Metal Industries, Ltd.) at 190° C. The hardness, permanentcompression set and tensile properties of the resulting sheet weremeasured by the methods described above. The physical properties of thesheets are shown in Table 2.

The vibration damping properties of the thermoplastic elastomercompositions obtained in Examples 3 and 5, and Comparatives Example 1, 3and 4 were evaluated by dynamic viscoelasticity described above. Theresults are shown in Table 1 and Table 2. TABLE 1 Example 1 Example 2Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9First Component APIB Parts by 100 100 100 100 100 100 100 100 100 step(A) weight SIBS1 Parts by 400 150 66 25 11 11 11 11 11 weight Cross-Parts by 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 linking weight agent Cross-μl/40 g 5 9 14 18 20 20 20 20 20 linking catalyst Second Component Partsby 100 100 100 100 100 100 100 100 100 step (A) weight Component PP1Parts by 20 20 20 20 20 — — — — (B) weight PP2 Parts by — — — — — 25 2535 50 weight OIL Parts by — — — — — 10 40 40 40 weight Hardness(JIS-A/immediately 61 57 62 58 65 70 60 68 75 after press) Permanentcompression set % 68 64 52 47 31 — — — — (70° C. × 22 hours) Permanentcompression set % — — — — — 26 23 39 48 (100° C. × 22 hours) Tensilestrength at break MPa 10.7 10.0 10.3 7.5 5.2 5.1 2.6 3.9 5.3 Tensileelongation at break % 470 530 530 490 480 370 270 300 300 tan δ (−20°C.) — — 0.75 — 0.62 — — — — tan δ (0° C.) — — 0.57 — 0.43 — — — — tan δ(20° C.) — — 0.30 — 0.24 — — — —

TABLE 2 Comparative Comparative Comparative Comparative Example 1Example 2 Example 3 Example 4 PP1 Parts by weight — 20 20 20 OIL Partsby weight — — 70 70 SIBS1 Parts by weight 100 100 — — SEBS Parts byweight — — 100 — SEPS Parts by weight — — — 100 Hardness(JIS-A/immediately 46 65 61 60 after press) Permanent compression set %80 75 37 36 (70° C. × 22 hours) Permanent compression set % 98 90 — —(100° C. × 22 hours) Tensile strength at break MPa 12.6 11.4 15.6 15.5Tensile elongation at break % 520 460 720 830 Tan δ (−20° C.) 0.88 —0.33 0.24 Tan δ (0° C.) 0.36 — 0.18 0.15 Tan δ (20° C.) 0.24 — 0.11 0.10

As is apparent from the results shown in the tables described above, thethermoplastic elastomer compositions of Examples 1 to 5 of the presentinvention have improved permanent compression set as compared with thecomposition comprising SIBS (Comparative Example 1) and the compositioncomprising SIBS and PP1 (Comparative Example 2) of the prior art. InExamples 6 to 9, flexibility and satisfactory permanent compression setcan be maintained by the addition of the plasticizer even if the amountof PP2 increases. As compared with the compositions of ComparativeExample 3 and Comparative Example 4 of the prior art, the compositionsof Example 3 and Example 5 have identical permanent compression set andare excellent in vibration damping properties.

EXAMPLES 10 TO 24

In the same manner as in Examples 1 to 9, sheets of the thermoplasticelastomer composition were formed according to the formulations shown inTable 3, and then the hardness, permanent compression set and tensileproperties were measured by the methods described above. The physicalproperties of the sheets are shown in Table 3.

COMPARATIVES EXAMPLES 5 TO 8

In the same manner as in Comparative Examples 1 to 4, sheets of thethermoplastic elastomer composition were formed according to theformulations shown in Table 4, and then the hardness, permanentcompression set and tensile properties were measured by the methodsdescribed above. The physical properties of the sheets are shown inTable 4. TABLE 3 Example Example Example Example Example Example ExampleExample 10 11 12 13 14 15 16 17 First Component APIB Parts by weight 100100 100 100 100 100 100 100 step (A) PP2 Parts by weight 11 11 11 — — —11 — PE1 Parts by weight — — — 11 11 11 — 11 PE2 Parts by weight — — — —— — — — PE3 Parts by weight — — — — — — — — OIL Parts by weight 40 40 4040 40 40 40 40 Cross- Parts by weight 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2linking agent Cross- μl/40 g 16 16 16 16 16 16 16 16 linking catalystSecond Component Parts by weight 100 100 100 100 100 100 100 100 (A)step Component PP2 Parts by weight 19 12 6 — 7 13 32 — (B) PE1 Parts byweight — 7 13 19 12 6 — 32 OIL Parts by weight 26 26 26 26 26 26 73 73Final APIB Parts by weight 100 100 100 100 100 100 100 100 compositionPP2 Parts by weight 40 29 20 11 20 60 PE1 Parts by weight 11 20 40 29 2060 PE2 Parts by weight PE3 Parts by weight OIL Parts by weight 80 80 8080 80 80 150 150 Hardness (JIS-A/immediately 61 62 63 60 62 62 58 64after press) Permanent compression set % 42 31 29 19 23 27 44 31 (100°C. × 22 hours) Tensile strength at break MPa 3.4 3.4 3.4 3.1 3.9 3.6 2.62.3 Tensile elongation at break % 360 340 350 330 400 400 340 270Example Example Example Example Example Example Example 18 19 20 21 2223 24 First Component APIB Parts by weight 100 100 100 100 100 100 100step (A) PP2 Parts by weight 11 — — — — — — PE1 Parts by weight — 11 2525 PE2 Parts by weight — — — 25 — — 25 PE3 Parts by weight — — — — 25 —— OIL Parts by weight 150 150 80 80 80 40 40 Crosslinking agent Parts byweight 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Crosslinking μl/40 g 9 9 11 11 11 1414 catalyst Second Component Parts by weight 100 100 100 100 100 100 100(A) step Component PP2 Parts by weight 19 — 7.3 7.3 7.3 9 9 (B) PE1Parts by weight — 19 — — — — — OIL Parts by weight — — — 66 66 FinalAPIB Parts by weight 100 100 100 100 100 100 100 composition PP2 Partsby weight 60 11 15 15 15 15 15 PE1 Parts by weight 49 25 25 PE2 Parts byweight 25 25 PE3 Parts by weight 25 OIL Parts by weight 150 150 80 80 80150 150 Hardness (JIS-A/immediately after press) 58 60 63 58 50 60 51Permanent compression set (100° C. × 22 % 42 33 23 23 29 33 24 hours)Tensile strength at break MPa 1.6 1.8 3.1 2.6 1.4 1.8 1.3 Tensileelongation at break % 130 190 380 430 260 190 260

TABLE 4 Comparative Comparative Comparative Comparative Example 5Example 6 Example 7 Example 8 SIBS2 Parts by weight 100 100 100 100 PP2Parts by weight 40 — 60 — PE1 Parts by weight — 40 — 60 OIL Parts byweight 80 80 150 150 Hardness (JIS-A/immediately 54 51 57 54 afterpress) permanent compression set % 88 80 84 80 (100° C. × 22 hours)Tensile strength at break MPa 3.4 3.0 1.7 1.7 Tensile elongation atbreak % 450 440 260 270

The final compositions of Examples 10 to 15 and Examples 20 to 22comprise 40 parts by weight of the total amount of olefinic resin and 80parts by weight of the softener based on 100 parts by weight of APIB.The compositions of Comparative Examples 5 and 6 comprise the samecomponents, except that APIB is replaced by SIBS. As is apparent from acomparison between them, all thermoplastic elastomer compositions of thepresent invention are excellent in permanent compression set regardlessof the same hardness (flexibility) . This fact shows that the effect ofthe present invention is exerted even when the olefinic resin is randompolypropylene, high-density polyethylene, and a mixture thereof. Thesame fact is confirmed in a comparison between the compositions ofExamples 16 to 19 and the compositions of Comparative Examples 7 and 8with a large proportion of the olefinic resin and the softener.

As is apparent from the compositions of Examples 20 to 24, when theolefinic resin is high-density polyethylene, low-density polyethyleneand linear low-density polyethylene, excellent permanent compression setwas obtained and the effect of the present invention was confirmed incase of various olefinic resins.

As compared with the composition of Example 10 wherein only randompolypropylene was used as the olefinic resin, the compositions ofExamples 11 to 15 wherein a portion or all of the olefinic resin ishigh-density polyethylene are excellent in permanent compression set.Therefore, the effect of the present invention is most remarkable whenusing polyethylene as the olefinic resin. In case of the compositions ofExample 16 to 19 with a large proportion of the olefinic resin and thesoftener, the same results are obtained.

INDUSTRIAL APPLICABILITY

The thermoplastic elastomer composition of the present invention can bemolded by the molding method and the molding apparatus employed commonlyfor thermoplastic resins and can be melt-molded, for example, byextrusion molding, injection molding, press molding, blow molding or thelike. The thermoplastic elastomer composition of the present inventioncan be effectively used to produce sealing materials such as packingmaterials, sealants, gaskets and plug, and dampers for optical driving,insulators for hard disk driving devices, dampers for civil engineeringand construction, damping materials for automobiles, damping materialsfor railway vehicles, damping materials for domestic appliances,vibration-proof materials, automotive interior materials, cushioningmaterials, daily necessities, electric parts, electronic parts, sportingequipments, grips, shock absorbing materials, electric wire coatingmaterials, packaging materials, various containers and writing materialsbecause of its excellent moldability, flexibility, vibration dampingproperties, gas barrier properties and permanent compression set.

1. A thermoplastic elastomer composition comprising: (A) a compositionobtained by crosslinking an isobutylene polymer having an alkenyl groupat the molecular ends with a hydrosilyl group-containing compound whilemelt-kneading in the presence of at least one kind selected from thegroup consisting of an aromatic vinyl-containing thermoplastic elastomerand an olefinic resin, and (B) at least one kind selected from the groupconsisting of an aromatic vinyl-containing thermoplastic elastomer andan olefinic resin.
 2. The thermoplastic elastomer composition accordingto claim 1, wherein the content of at least one kind selected from thegroup consisting of an aromatic vinyl-containing thermoplastic elastomerand an olefinic resin is from 5 to 100 parts by weight based on 100parts by weight of the isobutylene polymer having an alkenyl group atthe molecular ends in the component (A).
 3. The thermoplastic elastomercomposition according to claim 1, wherein the content of the component(B) is from 5 to 100 parts by weight based on 100 parts by weight of thetotal amount of the component (A).
 4. The thermoplastic elastomercomposition according to claim 1, which further contains a softener (C)in the amount of 1 to 300 parts by weight based on 100 parts by weightof the isobutylene polymer having an alkenyl group at the molecular endsin the component (A).
 5. The thermoplastic elastomer compositionaccording to claim 1, wherein an allyl group is introduced into themolecular ends of the isobutylene polymer having an alkenyl group at themolecular ends in the component (A) by a substitution reaction ofallyltrimethylsilane and chlorine.
 6. The thermoplastic elastomercomposition according to claim 1, wherein the isobutylene polymer havingan alkenyl group at the molecular ends in the component (A) is a polymerwhich has a number average molecular weight of 1,000 to 500,000 and hasat least 0.2 alkenyl groups per one molecule at the molecular ends. 7.The thermoplastic elastomer composition according to claim 1, whereinthe isobutylene polymer having an alkenyl group at the molecular ends inthe component (A) is a polymer having 50% by weight or more ofisobutylene.
 8. The thermoplastic elastomer composition according toclaim 1, wherein the aromatic vinyl-containing thermoplastic elastomerin the components (A) and (B) is a block copolymer comprising a polymerblock (a) composed mainly of an aromatic vinyl compound and a polymerblock (b) composed mainly of isobutylene.
 9. The thermoplastic elastomercomposition according to claim 8, wherein the aromatic vinyl-containingthermoplastic elastomer in the components (A) and (B) is a blockcopolymer is a triblock copolymer which has a structure comprising apolymer block (a) composed mainly of an aromatic vinyl compound—apolymer block (b) composed mainly of isobutylene—a polymer block (a)composed mainly of an aromatic vinyl compound, and has a weight averagemolecular weight of 40,000 to 200,000.
 10. The thermoplastic elastomercomposition according to claim 1, wherein the olefinic resin in thecomponent (A) is polypropylene.
 11. The thermoplastic elastomercomposition according to claim 1, wherein the olefinic resin in thecomponent (A) is polyethylene.
 12. The thermoplastic elastomercomposition according to claim 1, wherein the olefinic resin in thecomponent (B) is polypropylene.
 13. The thermoplastic elastomercomposition according to claim 1, wherein the olefinic resin in thecomponent (B) is polyethylene.
 14. The thermoplastic elastomercomposition according to claim 10, wherein the olefinic resin in thecomponent (A) is random polypropylene.
 15. The thermoplastic elastomercomposition according to claim 11, wherein the olefinic resin in thecomponent (A) is high-density polyethylene.
 16. The thermoplasticelastomer composition according to claim 12, wherein the olefinic resinin the component (B) is random polypropylene.
 17. The thermoplasticelastomer composition according to claim 13, wherein the olefinic resinin the component (B) is high-density polyethylene.
 18. The thermoplasticelastomer composition according to claim 4, wherein the softener (C) isparaffinic oil.